The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Multiple speed automatic transmissions are the overwhelming transmission choice for purchasers of passenger cars, sport utility vehicles and light trucks.
In such a typical automatic transmission, a hydraulic pump provides pressurized hydraulic fluid (transmission oil) to a valve body containing a plurality of spool valves, solenoid valves and passageways which collectively direct properly sequenced flows of pressurized hydraulic fluid to a plurality of actuators associated with clutches and brakes. The mechanical portion of the automatic transmission includes a plurality of planetary gear assemblies which are (1) interconnected by permanent coupling members, (2) selectively interconnected by the friction clutches or (3) selectively grounded by the brakes. Specific combinations of the clutches and brakes are engaged or activated in sequence to provide a predetermined sequence of numerically related gear ratios and thus output speeds and torques.
Increasingly demanding efficiency, performance and economic goals continue to encourage automatic transmission research and development. Because they so closely match the power and torque outputs of an engine to vehicle speed and load, there has been of late both increased development of and consumer demand for six, seven and eight speed automatic transmissions which provide significant performance enhancements and fuel consumption reduction. Nonetheless, such transmissions are known to have drawbacks. Two known and related drawbacks are complexity which often manifests itself as increased size and cost. Because of their benefits, there is ongoing development efforts directed to further improvements in automatic transmissions. The present invention provides such further improvements in automatic transmissions.